Electrode Material Effect on Submerged Arc Breakdown of Methylene Blue in Aqueous Solutions
N. Parkansky1, A. Vegerhof1, E. Faktorovich-Simon1, B. Alterkop1, O. Berkh2, and R. L. Boxman1
1Electrical Discharge and Plasma Laboratory, Tel Aviv University, Israel
2School of Electrical Engineering, Tel Aviv University, Israel
Abstract— Recently, submerged arc (SA) decomposition of Methylene Blue (MB) dissolved in water was demonstrated. However, the effect of particles eroded from the arc electrodes the MB decomposition, and their composition, has not been studied. The objectives of this research were to characterize the eroded particles and determine their effect on the decomposition of MB in aqueous solutions. Electrodes of various combinations of C, Fe, Ti were used. The treated solutions were examined with absorption spectroscopy. The produced particles were studied by XRD. It was obtained with a carbon anode (Ca) and an iron cathode (Fec) that the MB concentration decreased exponentially, while with the opposite polarity it initially decreased faster, but later saturated. The MB degradation behavior attained with Ca/Cc electrodes was like that of Ca/Fec, and with Fea/Fec. electrodes, like Fea/Cc, i.e. the anode material determined the MB decomposition behavior. The phenomenon may be explained taking in account that the anode erosion is usually significantly larger than the cathode erosion. It was shown that cyclic filtering of the Fe erosion particles during SA treatment with Fe electrodes exponentially decreased the MB concentration at the same high rate as observed initially without filtering, throughout the treatment period. Hence, removal of the accumulation of Fe particles during processing eliminated the cessation of the MB decontamination. In contrast, eroded Ti particles in an SA with Ti electrodes contributed positively to MB decomposition. Adding particles produced by an SA in solution without dissolved MB, to an MB-containing solution led to almost complete decomposition of the MB, as did an SA between Ti electrodes.
Keywords— Submerged arc, electrode material, water treatment, plasma, decontamination